From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexandre Oliva <oliva@dcc.unicamp.br>
To: Michael Lee <leemich@ms.com>
Cc: egcs-bugs@cygnus.com
Subject: Re: bug report
Date: Fri, 20 Nov 1998 14:08:00 -0000
Message-id: <orr9uyaulc.fsf@araguaia.dcc.unicamp.br>
References: <36550100.769A3CBB@ms.com>
X-SW-Source: 1998-11/msg00584.html
List-Id: <gcc-bugs.sourceware.org>

On Nov 20, 1998, Michael Lee <leemich@ms.com> wrote:


> class Derived: virtual public Base {

>     cout << reinterpret_cast<Derived*>(dp)->status() << endl;

> Segmentation Fault (core dumped)

You want dynamic_cast, not reinterpret_cast.  reinterpret_cast just
tells to compiler to interpret the Base* as if it were a pointer to
Derived*, *without* performing the needed conversions.  You'll also
have to make the base class polymorphic, by declaring some of its
methods virtual (e.g., the destructor)

> If you take out virtual from and change it to "class Derived: public
> Base {", it works.

It works by chance, just because the offset of the Base class is
zero in this case.

-- 
Alexandre Oliva  http://www.dcc.unicamp.br/~oliva  aoliva@{acm.org}
oliva@{dcc.unicamp.br,gnu.org,egcs.cygnus.com,samba.org.au}
Universidade Estadual de Campinas, SP, Brasil